Lost speed after change my lower unit

[admin]

The numbers don't make a lot of sense. You should be running much more rpm than that with that size prop. The original prop should lower your RPM's even more. I would recommend doing a compression test on the motor, and also making sure that you are getting full throttle on the engine as it sounds like the motor is not making enough power.

Tech Support

[cmchb1]

I had already think like you and I did the Compress test. The results: 100 psi in each cylinder. I will check the throttle. I am going to test prop today. Let you know my results.

[cmchb1]

Believe it or not with 15 1/4 x 19 I got 5100 rpm 43 mph. I already spoke with the person who sold me the prop. He is change it for a 15 1/4 x 21 to check it out.

[cmchb1]

You were totally right. After your observation of something else happening to the eng. I did take it to a Yamaha dealer for check up and they found out the eng was running in 5 cylinders. They rebuild the carbs and now I have the same speed than before. I am getting with a 15x19 prop, (top speed 5400rpm), 49 mph.

[admin]

Good, glad to hear your back up and running.

Tech Support